NCIS actress Lauren Holly will also appear on the Syfy drama as a senator with a hidden agenda.

Summer Glau - who appeared in the show's first season as Skylar Adams - will additionally reprise her role for three season two episodes.

Southland's C Thomas Howell has also been lined up for a guest role, playing a man with super speed. Meanwhile, Caprica's John Pyper-Ferguson will reprise his role as Stanton Parrish, and CSI: NY's Kathleen Munroe will reappear as Dr Rosen's (David Strathairn) daughter Dani.

Former Eureka co-executive producer Matt Hastings has joined Alphas for the new season.

The series returns to Syfy on Monday, July 23 at 10/9c. In the UK, the series airs on 5*.